Moreover, to date, various kinds of chelating agents, ion exchange materials, alkalizing agents, and dispersants have been known to be used for builders which are blended in detergents. Particularly, the phosphoric acid-based chelating agents comprising tripolyphosphates as a main component thereof have good water solubility and detergency, so that they have been formulated as main detergent builder ingredients.
In recent years, however, the use of tripolyphosphates has been decreased, since they are liable to cause eutrophication in closed water areas such as lakes and marshes. Instead, crystalline aluminosilicates (zeolites) have been commonly used as substitutes for the metal ion capturing agent, as typically disclosed in Japanese Patent Laid-Open No. 50-12381, of which the disclosure is incorporate herein by reference. Such detergents formulating zeolites as mentioned above would require a standard amount of dosage of 40 g per one washing cycle, the washing cycle being most commonly using about 30 L of the washing liquid per one cycle in Japan. Also, the powder detergents available at that time had a low bulk density at a level of 0.20 to 0.45 g/ml owing to the solubility in cold water. As a result, the standard volumetric amount is made as high as about 90 to about 200 ml of detergents per 30 L of water for washing, so that distribution is cumbersome between shops and households.
Therefore, an intense investigation has been made to produce compact detergents. For instance, Japanese Patent Laid-Open Nos. 62-167396, 62-167399, and 62-253699, of which the disclosure is incorporated herein by reference, disclose a remarkable decrease in the amount of crystalline inorganic salts such as sodium sulfate used as powdering aids conventionally contained in detergents. In addition, Japanese Patent Laid-Open Nos. 61-69897, 61-69899, 61-69900, and 5-209200, of which the disclosure is incorporated herein by reference, disclose that an increase in the bulk density of the detergents. By these findings, detergents having a bulk density of from 0.60 to 1.00 g/ml, whose standard a concentration is from 25 to 30 g/30 L, can be produced, thereby resulting in making the detergents compact to a level of a standard volumetric amount of from 25 to 50 ml/30 L.
On the other hand, crystalline alkali metal silicates having particular structure disclosed in Japanese Patent Laid-Open Nos. 5-184946 and 60-227895, of which the disclosure is incorporated herein by reference, shows not only good ion exchange capacity but also the action of the alkalizing agents (alkalizing ability). Therefore, possibility of more compact detergents has been studied because both of the functions which conventionally have been satisfied by two different components, including metal ion capturing agents, such as zeolites, and alkalizing agents, such as sodium carbonate, can be satisfied with the above crystalline alkali metal silicates alone.
For instance, Japanese Patent Laid-Open No. 6-116588, of which the disclosure is incorporated herein by reference, is concerned with a detergent composition containing a crystalline alkali metal silicate. In Examples of this publication disclosing a more compact detergent, even in a case where the amount of the detergent composition at washing is reduced by 25% by weight, the detergent composition has a washing power substantially the same as conventional detergent compositions. However, the composition is formulated based on the conventional washing principle, wherein the mainstream of the technical idea has been to make the oily components in dirt soluble by surfactants, and the composition is obtained by simple replacement of the alkalizing agent and the ion exchange material with the crystalline alkali metal silicate. Therefore, the ion exchange capacity are ascribed solely to the crystalline alkali metal silicates contained therein, so that the ion exchange capacity is insufficient for that needed for detergent compositions. In this case, the functions of the crystalline alkali metal silicates as alkalizing agents are prioritized over their functions as metal ion capturing agents, so that the washing power of the detergent composition is not always satisfactory, owing to the fact that the washing power of the detergent composition is dependent upon the water hardness of water for washing. Therefore, if the amount of dosage of the detergent composition were reduced, a good washing power is not able to be maintained.
A number of patent applications have been filed concerning the crystalline silicates disclosed in Japanese Patent Laid-Open No. 60-227895, of which the disclosure is incorporate herein by reference. Japanese Patent Unexamined Publication No. 6-502199, of which the disclosure is incorporate herein by reference, discloses a detergent comprising a layered crystalline silicate, a zeolite, and a polycarboxylate in particular proportions, to thereby provide a detergent which is free from providing film layer formation on fibers and has excellent washing power and bleaching agent stability. However, under the blending conditions given in this publication, when the amount of the detergents added was reduced at washing, the alkalizing ability is deficient because the amount of the crystalline alkali metal silicate in the builder composition is small, thereby making it impossible to maintain good washing power. Also, this publication never teaches the technical idea that an excellent washing power is exhibited in a small amount of dosage of detergents.
The technical idea that an excellent washing power is exhibited in a small amount of dosage of detergents as in the present invention cannot be found for detergents containing crystalline alkali metal silicates (crystalline layered silicates) disclosed in Japanese Patent Unexamined Publication 6-500141, Japanese Patent Laid-Open Nos 2-178398 and 2-178399, each of which the disclosure is incorporate herein by reference. Rather, in the case where the amounts of the detergent compositions shown in each of Examples are reduced, the washing power is lowered.
Japanese Patent Laid-Open No. 7-53992, of which the disclosure is incorporate herein by reference, discloses that the amount of dosage per cycle is reduced by formulating the layered crystalline silicate disclosed in Japanese Patent Laid-Open No. 60-227895, together with other builder components such as alkalizing agents and metal ion capturing agents, wherein the layered crystalline silicate is added in excess to the builder components. The technical idea disclosed herein is a conventional idea simply rephrasing that the alkalizing agents and the metal ion capturing agents added as two components are substituted with a single component of the crystalline alkali metal silicate, never suggesting any problems concerning a decrease in detergency after long-term storage.
In the prior art described above formulating the crystalline layered silicates, namely the crystalline alkali metal silicates, to the detergent compositions, the compositions are not known to have sufficient detergency. Moreover, when large amounts of the crystalline alkali metal silicates are formulated in powder detergents comprising anionic surfactants as the base surfactant components, the powder properties after a long-term storage and the detergency are likely to be lowered.
Accordingly, an object of the present invention is to provide a detergent composition for clothes washing exhibiting excellent detergency and undergoing remarkably little deterioration after a long-term storage.
These and other objects of the present invention will be apparent from the following description.